Revegetation in the 1914-1915 devastated area of Lassen Volcanic National Park PublicDeposited

Descriptions

At the time of the eruptions of Lassen Peak in 1914-1915, an
area of vegetation along the east slope of the mountain approximately
1 1/4 miles wide and four miles long was destroyed. Except for a
few surviving trees, all vegetation was destroyed.
A study of the revegetation of this rather unique area has
been made to determine, if possible, how vegetation re-enters such
a sterile area. Since this site is probably the only area in western
North America, outside of Alaska and Mexico, to have been devastated
by volcanic action in modern times, the results should bear
significance.
Two principal data-collecting methods were used. First,
29 regions (or stands) were selected throughout the present Devastated
Area for observation and description. Such information as
presence of species, density, size, edaphic factors and successional
stage was recorded for each. To interrelate these regions for showing
gradients in relation to each other or in relation to the undisturbed
marginal vegetations, a number of belt transects was laid
out. Woody vegetation was recorded along these six-foot wide belts.
Results of the study show that the predisturbance meadows
are being taken over by trees and shrubs, largely because of mud-flow influence. Successional stages occur in most locations where
Lodgepole Pine has become established. White Fir and White Pine
or Jeffrey Pine appear to be replacing it.
Island vegetations are established and appear to be serving
as radiation centers for new growth. "Stump sprout" survivor
Mountain Hemlock and Red Fir trees comprise part of the high elevation
vegetation from which stands may extend. Pits or craterlets
caused by hot rocks in the mudflow still exist and now provide protected
sites for revegetation on harsh, exposed slopes,
A definite zonation pattern now exists along the elevational
gradient of the central part of the Devastated Area starting with
Lodgepole Pine at an elevation of 6250 feet and terminating with Red
Fir and Lodgepole Pine at between 7500-8000 feet.
New growth along the north and south margins is variable.
At upper levels, invasion by old species is very slow. The greatest width of vigorous marginal growth occurs at an elevation of 7500-7700 feet along the south boundary where White Fir, Red Fir,
White Pine and Mountain Hemlock have all penetrated the new area
to a width of 400 yards.
Downslope "shift" is noted in regard to Mountain Hemlock
and Red Fir at higher elevations at the margins. Establishment of
montane species by upslope "shift" in the central regions appears
to provide necessary cover for establishment of the cold and shade
tolerant subalpine species in these central locations.
Several zones of soil instability still exist. One is a new
mudflow caused by stream action where vegetation penetrates this
zone marginally. Pioneer herbaceous forms are appearing rapidly
here.
Large dark-colored volcanic rocks carried by the mudflow
encourage revegetation by (1) absorbing heat from the sun in early
spring before the snow is melted and (2) protecting plants from extreme
winds and temperatures. Vegetation appears also to be related
to the snow-melt pattern along higher slopes.
Transitional gradients are common at the margins and in
some cases extend across the area. A young Jeffrey Pine climax
vegetation is now established across the Devastated Area at the Hot
Rock and Log Pile Region adjacent to the lower Lost Creek.
Photographs were used for relating former vegetation to
that of the present. A total of 121 species of plants was collected
and determined from the Devastated Area.